American Society for Clinical Pathology (ASCP) Technologist in Cytogenetics certification (ASCP CG) Practice Test

If a technician cannot get the metaphase into focus, what is the most likely issue?

1. The magnification is set too low

2. The camera is not parfocal with the microscope

3. The light source is insufficient

4. The slide is not properly positioned

The correct answer is: The camera is not parfocal with the microscope

The scenario where a technician cannot get the metaphase into focus is often related to issues with the optical setup of the microscope. The most likely issue in this case pertains to the camera not being parfocal with the microscope. Parfocality is an important feature of microscopes that allows for lenses to remain in focus when changing from one objective to another. If the camera is not parfocal, the image may shift in focus when the technician tries to utilize the camera for capturing the metaphase, making it difficult to achieve a clear and focused image of the chromosomes. Other options, while they may seem plausible, typically do not explain the inability to focus specifically on the metaphase stage. For instance, an improper magnification setting may cause images to be too small or blurry, but it would not necessarily prevent focusing entirely. Similarly, a less than optimal light source could affect brightness and visibility but would not directly hinder the ability to bring the metaphase into focus if positioning and adjustments were correct. Lastly, although improper slide positioning can cause focusing issues, it doesn't specifically point to the focus problem associated with using a camera in conjunction with the microscope setup.